The invention relates generally to retroreflector devices, systems and methods.
Electrowetting has been a highly attractive modulation scheme for a variety of optical applications. For example, electrowetting has been used to provide optical switches for fiber optics, optical shutters or filters for cameras and guidance systems, optical pickup devices, optical waveguide materials, and video display pixels.
Retroreflectors are well known by those skilled in the art of conspicuity markings. Retroreflectors are most often comprised of glass beads or a truncated corner of a cube, with the latter exhibiting several-fold higher retroreflective efficiency. The term ‘retroreflection’ is refers to the scenario in which reflective light dominantly emerges parallel to the direction of the incident ray. As a result, an observer positioned next to the illumination source perceives a surface that can be greater than fifty times (>50×) brighter than a diffusely reflecting surface, such as paper. Retroreflectors are commercially found in sizes ranging from bulk optic scales (cm's) to micro-replicated polymer films with corner cubes that individually measure tens of microns.
Conventional switchable retroreflectors have been demonstrated for free-space communications. However, all conventional approaches, such as micro-electromechanics, are difficult to scale to the arrays sizes needed for visualization at a distance; and prior approaches, such as multiple-quantum wells, are typically limited to very narrow-spectrum infra-red. Therefore, scalability and wide-spectrum must be realized before naked eye and other applications can be pursued (e.g., consider the requirements for conventional retroflective traffic safety signs). Improved capability could prove useful for a variety of applications including, but not limited to, flashing safety markings (personal, road, or structural), surveying and range finding, free-space communications, active decorative films, and military friend-foe-identification.